there are definitely shortfalls (like the baggage allowance, which is the big one, IMO), but aside from that one big one, I think *G is too diluted at times. About a month ago I flew UA on SFO-IAD due to involuntary reroute and during boarding there were like a million *G pax who boarded during this "priority boarding" call. However, the third tier really does give a considerable "priority" in OW.